fix(driver): use flume instead of crossbeam

[Berrysoft]

Also cleanup the features. We don't need the selector.

[inklesspen1rus]

But why?

[Berrysoft]

No strong reasons.

• flume says that it's faster than crossbeam sometimes. Maybe I'll do a benchmark before merging.
• To remove a dependency.

[George-Miao]

Can you do a benchmark?

[Berrysoft]

I have done benchmarks.

fn compio(c: &mut Criterion) {
    let mut group = c.benchmark_group("asyncify");
    group.throughput(Throughput::Elements(1));

    group.bench_function("compio", |b: &mut Bencher| {
        let runtime = compio::runtime::Runtime::new().unwrap();
        b.to_async(&runtime)
            .iter(|| async { runtime.spawn_blocking(|| black_box(())).await.unwrap() });
    });

    group.finish();
}

However, it seems that crossbeam-channel is faster...

[inklesspen1rus]

I have done benchmarks.

fn compio(c: &mut Criterion) {
    let mut group = c.benchmark_group("asyncify");
    group.throughput(Throughput::Elements(1));

    group.bench_function("compio", |b: &mut Bencher| {
        let runtime = compio::runtime::Runtime::new().unwrap();
        b.to_async(&runtime)
            .iter(|| async { runtime.spawn_blocking(|| black_box(())).await.unwrap() });
    });

    group.finish();
}

However, it seems that crossbeam-channel is faster...

On which machine and OS?
Sometimes I get massive performance degradation/CPU utilization on single core server VMs due to crossbeam's spinlock.

Sadly but can't reproduce that on my own machine due to Desktop kernel settings and multicore nature.

[Berrysoft]

Windows on a laptop with 8 CPU cores (16 threads).

[inklesspen1rus]

Tested on single-core VM and flume performs much faster

Also, that was really hard to execute your benchmark and not to stuck. I think there is a bug with asyncify, when Runtime doesn't waking up when thread did its job or job is just not sent to threadpool.

[inklesspen1rus]

Seems like in multicore environment there are minimal difference on my machine

But if I pin benchmark on a single core, flume performs faster

Well.. Let's in?

[George-Miao]

LGTM